Answer. The International Astronomical Union (IAU) downgraded the status of Pluto to that of a dwarf planet because it did not meet the three criteria the IAU uses to define a full-sized planet. Essentially Pluto meets all the criteria except one—it “has not cleared its neighboring region of other objects.”

Is Pluto a planet or not?

According to the International Astronomical Union, the organization charged with naming all celestial bodies and deciding on their statuses, Pluto is still not an official planet in our solar system. ... Soon after Pluto was discovered in 1930, it was designated a planet, the ninth in our solar system.

Why is Pluto no longer considered a planet quizlet?

After reclassification in 2005, Pluto is no longer classified as a planet because it: Pluto's gravity has not cleared its orbit of other matter and therefore it no longer fits the modern definition of a planet.